package main

import (
	"context"
	"log/slog"
	"net"
	"os"
	"os/signal"
	"syscall"
	"time"

	"github.com/joho/godotenv"
	"go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc"
	"google.golang.org/grpc"
	"google.golang.org/grpc/peer"

	hav1 "gitea.nik4nao.com/nik/home-services/gen/ha/v1"
	grpcadapter "gitea.nik4nao.com/nik/home-services/ha-gateway/internal/adapters/primary/grpc"
	"gitea.nik4nao.com/nik/home-services/ha-gateway/internal/adapters/secondary/ha"
	"gitea.nik4nao.com/nik/home-services/ha-gateway/internal/app"
	"gitea.nik4nao.com/nik/home-services/ha-gateway/internal/config"
	"gitea.nik4nao.com/nik/home-services/ha-gateway/internal/telemetry"
)

// MEMO: auth is not implemented.
// Add one of the following before exposing this service to any untrusted network:
//   Option A — shared API key per client: unary + stream interceptors read
//              "authorization" from gRPC metadata and compare to a secret
//              from config. Good for small number of known clients.
//   Option B — mTLS (recommended): tls.Config with ClientAuth: RequireAndVerifyClientCert,
//              cert pool from the internal CA. Each client gets a cert from
//              cert-manager. No runtime auth dependency, identity in the cert CN/SAN.

// version is set at build time via -ldflags "-X main.version=<tag>".
var version = "dev"

func main() {
	// 1. Load .env if present (ignored in K8s where env vars come from Secrets/ConfigMaps).
	_ = godotenv.Load()

	// 2. Load and validate config.
	cfg, err := config.Load()
	if err != nil {
		slog.Error("config error", "err", err)
		os.Exit(1)
	}

	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGTERM, syscall.SIGINT)
	defer stop()

	// 3. Set up telemetry.
	shutdown, err := telemetry.Setup(ctx, cfg, version)
	if err != nil {
		slog.Error("telemetry setup failed", "err", err)
		os.Exit(1)
	}

	// 4. Build the secondary adapter.
	haClient := ha.NewClient(cfg)

	// 5. Build application services.
	entityApp := app.NewEntityApp(haClient)
	lightApp := app.NewLightApp(haClient)
	switchApp := app.NewSwitchApp(haClient)

	// 5a. Prime the discovery cache. Non-fatal — ListLights/ListSwitches will
	//     retry lazily on the first call if this fails (e.g. HA not yet ready).
	if err := lightApp.Refresh(ctx); err != nil {
		slog.Warn("initial light discovery failed, will retry on first request", "err", err)
	}
	if err := switchApp.Refresh(ctx); err != nil {
		slog.Warn("initial switch discovery failed, will retry on first request", "err", err)
	}

	// 6. Build the gRPC server with OTel stats handler and logging interceptors.
	srv := grpc.NewServer(
		grpc.StatsHandler(otelgrpc.NewServerHandler()),
		grpc.ChainUnaryInterceptor(loggingUnaryInterceptor),
		grpc.ChainStreamInterceptor(loggingStreamInterceptor),
	)

	// 7. Register services.
	hav1.RegisterEntityServiceServer(srv, grpcadapter.NewEntityGRPC(entityApp))
	hav1.RegisterLightServiceServer(srv, grpcadapter.NewLightGRPC(lightApp))
	hav1.RegisterSwitchServiceServer(srv, grpcadapter.NewSwitchGRPC(switchApp))
	hav1.RegisterEventServiceServer(srv, &grpcadapter.EventGRPC{})

	// 8. Start listener.
	lis, err := net.Listen("tcp", ":"+cfg.GRPCPort)
	if err != nil {
		slog.Error("listen failed", "err", err)
		os.Exit(1)
	}

	// 9. Serve in background.
	go func() {
		slog.Info("listening", "port", cfg.GRPCPort, "version", version)
		if err := srv.Serve(lis); err != nil {
			slog.Error("serve failed", "err", err)
		}
	}()

	// 10. Block until signal.
	<-ctx.Done()
	slog.Info("shutting down")

	// 11. Graceful stop, then flush telemetry.
	srv.GracefulStop()

	shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()
	if err := shutdown(shutdownCtx); err != nil {
		slog.Error("telemetry shutdown error", "err", err)
	}
}

func loggingUnaryInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
	start := time.Now()
	resp, err := handler(ctx, req)
	attrs := []any{
		"method", info.FullMethod,
		"duration", time.Since(start).String(),
	}
	if p, ok := peer.FromContext(ctx); ok {
		attrs = append(attrs, "peer", p.Addr.String())
	}
	if err != nil {
		attrs = append(attrs, "err", err)
		slog.ErrorContext(ctx, "rpc", attrs...)
	} else {
		slog.InfoContext(ctx, "rpc", attrs...)
	}
	return resp, err
}

func loggingStreamInterceptor(srv any, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
	start := time.Now()
	err := handler(srv, ss)
	attrs := []any{
		"method", info.FullMethod,
		"duration", time.Since(start).String(),
	}
	if p, ok := peer.FromContext(ss.Context()); ok {
		attrs = append(attrs, "peer", p.Addr.String())
	}
	if err != nil {
		attrs = append(attrs, "err", err)
		slog.ErrorContext(ss.Context(), "rpc stream", attrs...)
	} else {
		slog.InfoContext(ss.Context(), "rpc stream", attrs...)
	}
	return err
}